The deformation of the elastomer layers and thus of the spring elements is achieved in accordance with the invention by a pressure-generating device which is fully integrated into the spring element. The pressure is generated here by tensioning devices which are installed and attached outside the spring element and are in contact with the pressure-generating device in the spring element. The elastomer bearings or elastomer spring elements according to the invention are particularly suitable for use in bearings in rotor and gearbox designs of large wind turbines, but can also advantageously be employed in machine and vehicle construction.
Elastic spring elements are known and are employed in many areas of technology, principally for damping vibrations and forces. The spring element here has a defined stiffness which is pre-specified by the type, size, shape and number of the elastomer layers present and in general cannot be changed or cannot be changed significantly after installation of the spring element.
In the case of large wind turbines with outputs of more than 2 megawatts, multipoint bearings are frequently employed which have to absorb and sufficiently damp the in some cases strong forces and vibrations occurring, in particular in relation to rotor blades and rotor shaft. The elastic bearing elements must therefore have relatively high stiffness. It is desirable here to have available elastomeric bearings in which the spring stiffness can be regulated or adjusted, if necessary even after installation in a turbine or device.
An elastomer bearing with adjustable stiffness is known, for example, from EP 1 566 543. In this application, a spring element is disclosed in which an elastomer layer is located between a connection plate and an end plate and optionally one or more intermediate plates, where the connection plate has an aperture with a connection part, through which pressure can be exerted on the elastomer layer by means of a displacement element in the form of a hydraulic fluid or movable piston element, and thus results in a change in the spring length of the spring element. In an embodiment here, the movable piston element essentially consists of a pressure piston having a more or less bulky piston head, which is generally covered with a hard elastomer layer. This piston head is [lacuna] by a pressure screw, which passed through a separate metal piece, which is attached to the actual spring element, so that, on screwing into the hollow thread in the metal piece, the piston head is forced into the region of the displacement elastomer of the spring element.
The design of the spring element here is matched to the shape and size of the pressure piston, which has the consequence that the production of the spring element is correspondingly more complex and thus more expensive, since the spring element must have a hollow shape corresponding to the piston. In practice, it has been found, in addition, that a piston of this type, which must be passed through the separate metal piece, often jams on tightening/loosening, so that fine adjustment of the spring stiffness frequently proves difficult, or is sometimes even impossible. In addition, problems arose in the meantime with uniform pressure distribution on the elastomeric spring element.
The object was thus to provide a corresponding spring element which functions in an analogous manner, but does not have the known disadvantages described of the corresponding bearings of the prior art.
The object has been achieved by the provision of a spring element as described below and in the claims.